A radio transmitter
attached to the back of a Mormon cricket helps researchers determine its
movement in the field. Click the image for more information about
For Some Insects, It's Smart to Run With the Crowd
Peabody February 17, 2005
To the casual observer, the millions of swarming locusts that
descended on West Africa last year were like something straight out of a
science fiction novel. Several mile-wide bands of the voracious insects ate
their way through the region's crop lands, threatening to cause food shortages
and loss of income for local farmers.
Sword, an ecologist with the Agricultural Research Service, has an
explanation for why some insects, like the desert locust, Schistocerca
gregaria, gather in mind-boggling numbers and move together across the
In the current issue of the journal Nature, Sword describes how the
Mormon cricket--a species of katydid known to periodically overrun agricultural
fields in the Northern Plains of the United States--relies on the protection
afforded by thousands, if not millions, of its fellow crickets to reduce the
risk of attack by predators.
Researchers have speculated that insects moving in bands derive some
benefits from traveling en masse. But no one has previously attempted to
quantify those advantages, mostly because of the inherent difficulty in
tracking how individual insects move within a band of millions.
Sword, who works at the
Northern Plains Agricultural Research Laboratory in Sidney, Mont., teamed
with colleagues Patrick Lorch of the University
of North Carolina at Chapel Hill and Darryl Gwynne of the
University of Toronto at Mississauga
to use radio transmitters to monitor the movements of individual Mormon
crickets during a study last year near
Dinosaur National Monument in
The researchers discovered that for the crickets, there's safety in
large numbers. Those insects which were part of a large moving band were much
less likely to be eaten. In fact, 50 to 60 percent of the Mormon crickets that
were separated from a migratory band were killed within two days by predators
such as birds and rodents, while none of those staying with the band were
eaten. Radio transmitters belonging to those unfortunate, lone insects were
found either chewed or still glued to a partially-eaten cricket corpse.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.